Feature/b2b build hash vars

[CNanninga]

What/Why?

Builds on PR #2626

B2B Buyer Portal build filenames may include unique build hashes depending on the build configuration.

For the custom Buyer Portal loader script, this PR swaps out managing these build hashes in code for managing them with env vars.

[changeset-bot]

⚠️ No Changeset found

Latest commit: d1d6af5

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[vercel]

@CNanninga is attempting to deploy a commit to the BigCommerce Platform Team on Vercel.

A member of the Team first needs to authorize it.